Earth well borehole drilling and logging system



J. J. ARPS Feb. 16, 1960 EARTH WELL BOREHOLE DRILLING AND LOGGING SYSTEM Filed March 5. 1954 6 Sheets-Sheet l 2N NNN INVENTOR. J/L/ J 10Q/D5 J. J. ARPS Feb. 16, 1960 EARTH WELL BOREHOLE DRILLING AND LOGGING SYSTEM Filed March 5, 1954 6 Sheets-Sheet 2 I IUA. VIII. H.||||H Plv z La 3s a a W a a 5 a Feb. 16, 1960 J. J. ARPs EARTH WELL BoREHoLE DRILLING AND LOGGING SYSTEM Filed March 5. 1954 INVENTOR. JQA/ J. 102195 J. J. ARPS Feb. 16, 1960 EARTH WELL BOREHOLE DRILLING AND LOGGING SYSTEM Filed March 5. 1954 6 Sheets-Sheet 4 Feb. 16, 1960 J. J. ARPs 2,925,251

EARTH WELL BOREHOLE DRILLING AND LOGGING SYSTEM Filed March 5, 1954 6 Sheets-Sheet 5 nffm? a mf il ||||....I||||| ||||||i|||ll|||||| u. w o n .f o bf /W m /f -I+ llll l... Illl n IJCITIIIII l n ,.N. .n4 f u T f x IIIIIIII lllllullh l I l i l IIL Il ||I||||||ILl|llAl..I.I|Il|ll||||..Mllm- .M M 1 -J 1, 0 uw H Feb. 16, 1960 J. J. ARPS 2,925,251

EARTH WELL BOREHOLE DRILLING AND LOGGING SYSTEM Filed March 5. 1954 6 Sheets-Sheet 6 United States Patent O EARTH WELL BOREHOLE DRILLING AND LOGGING SYSTEM Jan J. Arps, Dallas, Tex.

Application March 5, 1954, Serial No. 414,381

29 Claims. (Cl. Z55-1.8)

This invention relates to drilling and logging of earth well boreholes, and more particularly to a system in which logging of an earth well borehole may be carried out simultaneously with the drilling of the borehole. The invention provides a system which makes it possible to transmit information regarding the drilling apparatus and borehole conditions and characteristics of the formations being drilled or traversed, without the necessity for electrical connections extending from the surface of the earth to the positions or locations in the borehole at which said information is produced or obtained, while drilling is in progress as well as during intervals between drilling periods, but with the drill string in the borehole.

It is customary practice in providing electrical logs of formations through which a borehole is drilled, to rst drill the hole, then remove the drilling equipment, and then lower into the borehole on an electrical cable certain electrodes which are connected to the surface of the earth by electrical connections. Through measurements of the ow of current through two electrodes the natural or self-potential of the formation surrounding the borehole may be indicated, and through impressing upon two such electrodes an electrical current, the conductivity of an earth path adjacent the electrodes may be indicated and the apparent specific resistance or impedance of the formations being logged may be determined. It is also possible to secure other electrical characteristics of the formation surrounding the borehole at the location where one of the electrodes may be situated.

Attempts have been made, as evidenced by certain patented prior art, to provide an electrical conductor leading from the electrode or electrodes within the borehole up through the drill stem to the surface of the earth such that drilling and logging operations might be carried out simultaneously. This latter system is not only expensive, but also introduces great likelihood of trouble in operation and is, for many obvious practical reasons, objectionable and, in so far as is known, no operations of this kind have ever been practicable or commercially successful.

The present invention provides a system for logging while drilling, in which system there is no necessity for an electrical conductor from the electrodes within the borehole being surveyed to the surface of the earth. The system of the invention also provides means for obtaining in the vicinity of the drill bit in the borehole, information other than that concerning the electrical characteristics of the earth formations, and for transmitting both types of information to the earths surface and there presenting visual and aural indications of the information, simultaneously, and while drilling, as well as during drilling stoppages with the drill string in the borehole; and without electrical conductors extending into the borehole.

In the following portion of the specification and in the claims hereto appended, the term logging is employed as a generic term to include not only the gath-` ICC ering or obtaining of information and the transmission thereof and the graphical recording of the information or parts of the information, but also the presentation of all or part of the information to any of the human perceptive senses. For example, the information could be presented for aural or visual perception, as by means of sound or mechanical indicators, or graphical recorders, or by a combination thereof, all of which are included in the term logging as herein employed.

It is, accordingly, an object of this invention to provide a borehole logging system which will be capable of electrically logging a borehole simultaneously with the drilling thereof, thereby not only eliminating the necessity of removing the drilling equipment and replacing it with the logging equipment and thus effecting a great saving in time, but also providing a means whereby an operator may tell at all times the nature of the formation through which he is drilling, instead of having to wait until the hole or well has been completed before obtaining this information. This enables an operator to cease drilling whenever a potentially productive formation is encountered.

It is also an object of the present invention to provide a borehole logging system whereby information relating to the electrical and other characteristics of the formation surrounding the hole being drilled may be communicated to the surface of the earth without the necessity for electrical conductors or other special information transmitting means extending from the bottom to the top of the well, other than the apparatus ordinarily used in drilling a well.

Another object of the invention is to provide a means whereby information regarding other conditions occurring or prevalent during drilling operations may be immediately communicated to the earths surface, such conditions including drill bit troubles such as excessive bit Wear and excessively high bit temperature, the presence of a drilling fluid leak or washout, a deviation or inclination of the borehole from a true vertical direction more than a predetermined degree, the application of excessive weight to the drill bit, and the production of excessively high torsional stress in the drill stem or string.

Another object of the invention is to provide an ef\ ficient earth borehole logging system capable of diversitied operation whereby there is rendered concurrently available at the top of the borehole during drilling an indication of a leak of drilling fluid from the drill string between the top of the string and a location adjacent the lower end of the string, and a depth-log of the electrical resistance of an earth path adjacent the lower end of the drill string.

Another object of the invention is to provide an earth well borehole logging system capable of diversified operation whereby information may be obtained at the top of the borehole concerning earth conductivity (or resistivity) at a location adjacent the borehole, and rate, of ow of drilling fluid through the drill collar during either rotation or absence of rotation of the drill string, and whereby inclination of the borehole from a true vertical direction in excess of a predetermined degree may be ascertained in absence of drill string rotation, and whereby drill bit trouble may be immediately detected at the top of the borehole during normal drilling operations and whereby excessive drill collar torsion or compression may be detected at the top of the borehole, all without resort to electric cable means extending into the borehole.

Another object of the invention is to provide an earth well borehole logging system having an ellicient and simple means for producing or propagating pressurechange signals in the drilling fluid stream in a drill string for transmission to, and detection at, the top of the borehole.

Other objects, advantages and features of novelty will be made evident hereinafter in a detailed description of the invention and in the appended claims. In the drawings which illustrate a preferred embodiment and mode of operation of the invention and modified forms of parts thereof, and in which like reference characters designate the same or similar parts throughout the several views:

Figure 1 illustrates diagrammatically a portion of the drilling equipment located at the earths surface and the apparatus for detecting and translating drilling fluid pressure-change signals propagated in the borehole;

Figure 2 depicts a partly diagrammatic vertical section through the upper portion of the drill collar, the drill collar and drill bit forming the lower portion of the drill string illustrated in part in Figure 1;

Figure 3 depicts a partly diagrammatic vertical section through the lower portion of the drill collar and drill bit arranged in such a manner that the bottom part of Figure 2 is a continuation of and joins with the top part of Figure 3;

Figure 4 is a cross sectional view of the drill collar taken on line 4-4 of Figure 2;

Figure 5 is a cross sectional view of the drill collar taken on line 5-5 of Figure 2 showing a valve therein 1n open position;

Figure 6 is a cross sectional view taken on line 5--5 of Figure 2 and similar to Figure 5, but showing the valve in closed position;

Figure 7 is a cross sectional view taken on line 7-7 of Figure 2 showing a valve therein in open position;

Figure 8 is a cross sectional view taken on line 7-7 of Figure 2 and similar to Figure 7, but showing the valve in closed position;

Figure 9 is an enlarged fragmentary vertical sectional view of a bit trouble detecting device, said device being comprised in the arrangement of Figure 3 and shown within the dash-line rectangle 9 therein;

Figure 10 is a diagram of the electric circuits and associated devices contained principally in the drill collar and located at the bottom of the drill string, the components being grouped according to their physical grouping in the drilling apparatus, as shown in Figures 2 and 3;

Figure ll is a graphical representation of a drilling fluid pressure signal transmitted from the apparatus within the drill collar and received, detected and translated at the top of the borehole;

Figure 12 is a graphical representation of the slowly varying background component of the drilling Huid pressure signal represented in Figure l1;

Figure 13 is a graphical representation of the so-called noise component of the drilling fluid pressure signal represented in Figure l1;

Figure 14 is -a graphical representation of the useful component of the signal represented in Figure 11;

Figure 15 is a graphical-representation of the output of the derivator network diagrammatically shown in the arrangement of Figure 1;

Figure 16 is a graphical representation of the signal output of the threshold network diagrammatically shown in the arrangement of Figure 1;

Figure 17 shows graphically the grid-voltage platecurrent characteristic of a variable mu tube as employed in the apparatus of Figure 18;

Figure 18 shows schematically the variable threshold network included in the arrangement of Figure l;

Figures 19 and 19a illustrate graphically the performance characteristics of the variable threshold network shown in Figure 18;

Figure 20 is a cross section similar to that of Figure 7 but illustrating on a larger scale a modified form of Valve in open position, and taken on a plane indicated by line 20-20 of Figure 20a;

Figure 20a is a fragmentary vertical sectional view taken on line 20a-20a of Figure 20;

Figure 21 is a cross sectional view of the valve apparatus shown in Figure 20 but in closed position, and taken on a plane indicated by line 21-21 of Figure 21a; and

Figure 21a is a fragmentary vertical sectional view taken on line 21a-21a of Figure 2l.

Referring now to the drawings, and primarily to Figures 1-10, and more specifically to Figures 1, 2 and 3, it may be seen that these figures depict schematic views, including a longitudinal or vertical section through a well being drilled in accordance with the method and with the apparatus of the invention. In accordance with conventional drilling practice a circulating uid termed rotary mud or simply drilling uid is employed to carry the drill cuttings out of the borehole as drilling proceeds. The upper portion of the borehole 10 is lined with a surface casing 11 which usually extends but a comparatively short distance into the well. At its upper end the casing 11 is provided with a side outlet pipe 12 for discharging drilling uid and cuttings into a conventional basin 13. Extending through the casing 11 and into the borehole 10 is a conventional hollow drill string 14, the lower portion of which comprises a drill collar 24 (Figures 2 and 3), to which is connected at its lower end a drill bit 15 having drilling uid discharge openings 15a adjacent the cutting teeth of the bit. A kelly 20 is connected to the upper end of the drill string and extends through a rotary table 21 mounted conventionally on the floor of the derrick and which is rotated by a conventional power rig or draw works (not shown) in order to effect rotation of the drill bit, all in a manner well known in the art. The upper end of the kelly is connected to the usual rotary swivel 19, and the entire drill string is suspended through the swivel from a traveling block 22 which is adapted to be raised and lowered in the derrick in accordance with conventional practice by well known means.

The apparatus for circulating or forcing the drilling tiuid to flow in a stream along a path down through the hollow drill string and up through the annular free space in the borehole comprises the basin 13 previously referred to, a settling pit 16, a suction pit 25 and a drilling liuid pump 426 having a suction pipe 27 extending into the suction pit, and a fluid discharge conduit or pipe 202 in communication with the drill string 14 through rotary hose 27a, swivel 19 and kelly 20.

As shown in Figures 2 and 3, there are positioned within the drill collar 24 two important components of the earth well borehole logging system herein described. One, a control component 26 which is contained within a suitable container 26b within a chamber 71, preferably of annular shape, consists essentially of a device for sensing or measuring the electrical conductivity (and hence the resistivity) of an earth path adjacent the lower end of the drill string, and for producing an information signal, preferably in the form of an electric current pulse, representing said conductivity or resistivity, as is more fully described hereinafter in connection with Figure 10. The other component, indicated generally at 427, is a transducer system responsive to said signal and to other signals hereinafter described, for correspondingly controlling the character of the drilling fluid flow therethrough to produce corresponding pressurechange signals in the drilling fluid stream for transmission therethrough to the top of the borehole.

The control of the character of the drilling fluid flow is elfected by control means including a novel valve which may be descriptively termed a squeeze valve which produces a localized increase in resistance to said drilling fluid flow therethrough in response to each one of said information signals. The increase in resistance to the flow of the drilling fluid causes a corresponding pressure-change signal in the form of a pressure rise or increase in the pressure in the drilling fluid stream that may be conveniently received, detected, and suitably translated into physical or sense-receptive indications at the top of the borehole by means of the instruments and apparatus shown in Figure 1. Consequently, by means of this arrangement, the driller may be continually informed as to the electrical resistivity of the formation being drilled, it being noted that said signals are normally being produced at somewhat closely spaced time intervals of variable duration, as will later be explained.

The lower portion of drill collar 24 is covered externally with a layer or coating of suitable electrical insulating material 28, such as rubber or Bakelite, upon which is positioned a series of replaceable cylindrical rings 29 made from a rubber with very high wear-resistance characteristics. The inside surface of the lower portion of drill collar 24, forming the drilling fluid stream path or passageway 30, is also similarly covered with a layer or coating of suitable insulating material 31. In order to further electrically insulate drill bit 15 and bit sub 32 from the main body of drill collar 24, a coneshaped adapter 33 is provided which is preferably made of a suitable nonconducting high-strength material and which is provided with internal and external threads to engage corresponding threads in the metal of bit sub 32 and drill collar 24. Positioned in the lower part of the drilling fiuid passageway 30 in the drill collar is a check valve 34 of conventional design which prohibits reverse or upward flow of drilling fluids through the drill collar, but offers comparatively little resistance to normal downward flow thereof. Positioned above this check valve 34 is a power unit 35 diagrammatically shown within the rectangular enclosure 35a. The check valve 34 serves to protect the power unit from various extraneous materials, such as fragments of rock, which are kept from being carried into the power unit through the passageway 30 when the drill string is lowered into the borehole.

The power unit 35 comprises a drilling fiuid driven turbine 37 of conventional design which, through shaft 38, drives an electrical generator 39 which generates pulsating electric current. The generator, with suitable leads as indicated in Figure l0, forms an electric power supply. An extension of shaft 38 makes a driving connection with a high-ratio gear speed reducer 40 which is preferably constructed in such a way that the output shaft 41 from this gear reducer rotates relatively slowly. The construction may be such, for example, that shaft 41 makes only one revolution for every million or more revolutions of shaft 38. Output shaft 41 from gear reducer 40 drives a wheel 42 provided with a cam 43. When this cam contacts a fixedly mounted spring 44, the latter is lifted to a position where electrical contact is made with a fixed contact 45. As soon as the rotation of shaft 41 has carried the cam past spring 44, electrical contact with connector 45 is again broken. The purpose of the speed reducer and cam-actuated contactor is to provide an indication of the flow of drilling fluid through the turbine, as will be more fully explained hereinafter.

The downward iiowing drilling fluid stream flows from the central bore 46 of the intermediate portion of drill collar 24 through passageway 47 to the turbine 37 from which it is discharged through passageway 48 into the central bore 49 `of the bottom portion of the drill collar 24. .Electric current generated by generator 39 passes through lead 50 to vertical rods 51a and 51b, 52a and 52b (see the lower part of Figure 2) into control cornponent 26 in chamber 26b through lead 53. A portion of drill collar 24 is formed with two preferably annular chambers 54 and 55 of substantial vertical length, which contain excessive torque and excessive weight switches or cut-out devices, respectively, to be more fully described hereinafter. The outer and inner concentric metal walls 56 and 57 of these openings are of lesser thickness than the rest of the drill collar, while still being strong enough to withstand the various forces exerted upon them during normal drilling operations. Rod 51a which forms a part of the beforementioned excessive torque switch mechanism is firmly held relative to the drill collar body at the bottom wall of chamber 54 by insulating material 58, while rod 51b is firmly held relative to the drill collar body at the top wall of chamber 54 by insulating material 59. The top end part of rod 51a is provided with a flattened, vertical extension 60, While the bottom end part of rod 51b is provided with a flattened, horizontal extension 61. The flattened extensions 60 and 61 are spaced apart laterally a short distance. Adjustable electrical contact between the two extensions is provided by means of a lateral set-screw 62 threaded through extension 60. Rod 52a which forms a part of the beforementioned excessive weight switch mechanism is firmly held at its bottom portion relative to the drill collar body at the bottom wall of chamber 55 in insulating material S9, while rod 52b is firmly held in a similar manner in insulating material 63 in the top wall of chamber 55. Rod 52a is provided at its upper extremity with a horizontal extension 64, while rod 52b is provided at its bottom end part with a U-shaped extension 65 which is positioned below and spaced a short distance from extension 64. Electrical contact between extension 64 and extension 65 can be made with vertically adjustable set-screw 66 which is threaded through extension 64.

Connected to rod 51a and hence to output lead 67 of generator 39 is a lead 68, which is electrically connected to a metal insert 69 of a maximum inclination cut-out or inclinometer switch device 70 (see Fig. l0). This maximum inclination cut-out device is mounted in the beforementioned annular chamber 71 in the drill collar, which chamber is filled with a suitable oil of fair.y high viscosity. Within this annular chamber is a metal pendulum 72 suspended freely at its upper end from a universal joint 73 which is fixedly mounted in insulation material 74. The bottom part of pendulum 72 is provided with a small spring-loaded carbon brush 75 which slides on the surface of metal insert 69. This metal insert 69 is embedded in and electrically insulated from the drill collar body by a fixed body of insulating material 76. When the inclination or deviation of the drill collar 24 from true vertical is less than a predetermined amount or degree and the drill string is not rotating, carbon brush 75 will be in contact with metal insert 69 and thereby conduct current from lead 68 to output lead 161 into control component 26 hereinafter more fully described.

The pressure-rise signal producing portion of the unit located in the drill collar, and indicated generally by ordinal 427 in Figure 2, comprises means including an elastic valve body 78 preferably formed of a suitable elastomer such as synthetic rubber and preferably though not necessarily of tubular internal conformation; the valve body being suitably secured to rigid structure in or forming part of the drill collar and defining, with preferably rigid structure in or forming part of the drill collar, a space or confined cavity 77 of preferably annular shape, and such space or cavity being fluid-tight and having as part of its boundary-defining area an area of one surface of the elastic valve body so that, when a fluid is forced under pressure into the cavity, the elastic valve body will be forced or flexed away from the opposite wall or boundary of the cavity, the cavity being thus enlarged in volume. The elastic valve body is so shaped and arranged that, when flexed in the manner mentioned, it will form a restriction in the ow path of the drilling uid stream flowing downwardly through the drill collar. In the preferred form, as illustrated in the drawings, the valve body 78 is, as stated, of tubular construction (see Figures 2, 5, 6 and 7, for example); at least a portion of the interior of the tubular body forming a portion of the boundary of the drilling uid stream, or dening a part of the drilling Huid passageway through the drill collar. Also, in the preferred form, a portion of the opposite or outside surface of the valve body forms at least a part of the interior boundary-defining wall of the aforementioned cavity 77. The cavity, preferably encircling or surrounding a substantial portion of the elastic valve body and hence preferably of generally annular shape or form, has the remainder of its boundary-forming wall or walls made of rigid pressure-resisting material and conveniently may be a part of the drill collar as depicted in the mentioned figures of the drawings, the cavity wall being provided, however, with openings into conduits or passages 80 and 8l whereby a body of control uid may enter or ow into, and exit from, the cavity. Also comprised in the pressure-rise signal producing portion of the aforementioned unit is means forming a control uid reservoir, designated by ordinal 79, which is formed to communicate with the passageways 80 and 81 and is conveniently formed as a cavity of generally annular form surrounding an inner wall of the drill collar immediately below the passageways 80 and 81, as depicted diagrammatically in Figure 2. As previously iudicated, cavity 77 and reservoir 79 are fluid-tight and are lled with a suitable control fluid such as, for example, oil or other hydraulic uid, or a suitable gas or mixture of uids. The control lluid may desirably be in most circumstances a relatively incompressible liquid of such characteristics that the normal increase in pressure due to the increasing weight of the drilling fluid above the drill collar in the borehole as the collar moves down in the borehole, is compensated approximately by the expansion of the control liquid due to the increase in temperature with depth as normally encountered in a borehole. Remaining small changes in control fluid volume due to compression and expansion when running the drill string into or out of the borehole may, if desired, be compensated by suitable means such as a Sylphon bellows 82. which is exposed to the pressure of the drilling lluid in the bore 46 on one side, and to the pressure of the control fluid in reservoir 79 on the other side.

As depicted in the drawings, squeeze valve body 78 comprises a tubular elastic body which is tightly attached at its opposite ends to the drill collar structure at the corresponding ends of the annular space or cavity 77 by suitable means including screws 83 in such a manner as to form an interconnecting passage of generally circular cross section and of variable external diameter between the upper and lower portions 100 and 46, respectively, ofthe drilling uid stream flow passageway through the drill collar, that is, the inner surface of the tubular elastic body forms a boundary for a length ofthe drilling lluid stream. The action of tubular elastic valve body 78 is such that when pressure or force is applied to the exterior surface thereof during ow of drilling fluid therethrough, the valve body will flex inwardly to form a restriction in the drilling uid stream path and thus increase the resistance to flow of drilling uid therethrough. Under some conditions the valve body may tend to completely collapse inwardly, and may remain so collapsed so long as drilling fluid flow continues. In order to preclude or restrict a complete collapse of the valve and complete closing of the drilling fluid passageway through its center under ordinary conditions of drilling iluid ow and pressure, the elastic valve body is K formed with a series of preferably elastic circumferentially spaced longitudinally extending and radially directed ribs 84 at the outside of the inner elastic tubular member forming the tubular portion of the valve body, as best shown in Figures 5 and 7. The ribs may be suitably secured to the central elastic tube portion of the valve body or formed integrally therewith. Figure 5 is a cross sectional view of the valve body and external ribs 84 at line 5-5 of Figure 2 when the yvalve is in open position, in which position the valve does not rc strict ow of drilling fluid therethrough. When the valve is open, ribs 84 are separated by longitudinally extending radially directed slots and the tube portion is undstorted and presents a smooth interior boundary for the drilling fluid stream. Figure 7, which shows a cross sectional view of the open squeeze valve body 78 taken on line 7-7 of Figure 2, illustrates that the slots 815 are of greater width at this section of the valve body than at the end whereby inward flexing of this section may exceed that near the end of the valve body. Thus, when external pressure is applied to the elastic valve body, it will normally liex inwardly or collapse until the ribs 84 have moved radially inwardly and are in side-to-side contact, each with its next adjacent neighbor ribs, causing the central elastic tube portion to distort and buckle or bulge inwardly in small, longitudlinally extending ridges adjacent the inner bottoms of slots 85, as indicated in Figures 6 and 8. Since the slots 85 are wider at the central portions, as at section 7-7, the remaining internal drilling fluid passage 86 in the center portion adjacent the section 7-7 will be of reduced diameter and much smaller than the remaining internal drilling fluid passage 87 in the end portions adjacent section 5 5, as may be noted from a comparison of Figures 6 and 8 which show sections of the valve in closed condition.

It is evident, therefore, that the valve body when thus inwardly ilexed will normally suffer an inner diametrical reduction and assume a smoothly curved choking shape when closed, as indicated by dashed lines 88 of Figure 2, although as before noted, under extreme conditions of pressure, and depending also upon the nature and pressure of the medium employed to apply the external pressure, the valve body may in collapsing assume a flattened, completely closed shape. For use under those ex treme conditions of service under which there is likelihood of complete collapse of the Valve body, a modified form of valve body is provided, as is more fully explained hereafter in connection with Figs. 20 and 21. Also, it is evident that the inner surface or face of the elastic valve body forms a confining boundary for at least a portion of the drilling liuid stream, and that the opposite or outer surface or face of the valve body presents au area for the application of pressure to cause the elastic body or member to ilex into the drilling uid stream or path to cause a restriction therein which acts to restrict the ow of drilling iiuid therethrough. This restriction, which is removed by removal of excess of pressure from the outer face of the elastic body and the elastic return of the valve body to normal position or attitude, causes or propagates a pressure change, in the form of a pressure rise, in the drilling fluid stream above the valve body. This pressure rise may be used asa signal, as it is quickly transmitted by and through the stream of drilling uid in the drill string to the surface of the earth and through the kelly and swivel to hose 27a and pipe 202.

A restriction 158 may be provided in the flow passage between the lower end of squeeze valve body 78 and bellows 82 to cause the pressure in the flowing drilling fluid stream to be lower opposite the bellows 82 than within the flow passage through the valve body 78 above the restriction 158. This pressure differential may be utilized to aid the natural resiliency of the valve body in returning the body to its normal position when the exing pressure is removed from its exterior as hereinbeforc described. It is obvious that when the valve body is in normal open position the pressure in the drilling fluid stream within the valve body must be balanced by a substantially equal opposing pressure applied to the exterior of the valve body to permit the latter to maintain normal position, and that an additional pressure component must agarran he added to the mentioned opposing pressure to cause flexing of the valve to closed position. For the sake of simplicity, this additional pressure component will be referred to simply as pressure hereinafter in this speciiication and in the claims. That is, the term pressure as employed to designate that which is applied to the exterior of the valve body to inwardly tlex the latter, is the gauge pressure with respect to the drilling uid stream pressure within the valve body.

An assembly comprising a pump 89 coupled to an electric driving motor 91 is shown diagrammatically at 90 (see Figure 2) and is arranged and adapted to continuously act as a force exerting means to force or pump the oil or control iluid under pressure from reservoir 79 through conduit or passageway 80 into cavity 77 as long as electrical power is supplied to motor 91. An electromagnetically operated self-opening control Huid valve 92, shown diagrammatically and indicated by ordinal V, is interposed in conduit or passageway 81 and is normally in open position, thereby allowing free or unrestricted passage of control fluid or liquid from cavity 77 through passageway 81 into reservoir 79. When an electric power or current pulse is supplied to electromagnet 94 of the control valve, the valve is thereby irst at least partly, and preferably completely, closed, restricting or cutting olf the return ilow of control iiuid from cavity 77 into reservo-ir 79, and subsequently is automatically opened to free the outlet at the termination of the electric current pulse. Actuation of valve 92 by magnet 94 while pump 89 is operated, will, therefore, cause an increasing pressure in cavity 77 outside valve body 78, which pressure will, in turn, cause the squeeze valve body 78 to flex inwardly as indicated by dashed lines 88, and propagate a pressure-rise signal in the drilling fluid stream. Electric power to operate pump 89 is supplied through lead 95 and power to operate valve 92 is supplied through electric circuits to be more fully described hereinafter.

As noted above, squeeze valve body 78 may, under extreme circumstances, tend to completely collapse. In some instances such complete collapse may be undesirable, and for such instances I have provided a modified type of squeeze valve having a means therein which prevents complete collapse of the valve body.

Referring now to Figures 20 and 21 which are fragmentary views in section of apparatus, there is illustrated within drill collar 24 a generally tubular elastic squeeze valve body 78a similar in external appearance to previously described squeeze valve body 78. Surrounding squeeze valve body 78a is an annular space 77a for the admission of control fluid such as oil, for the application of pressure to the exterior of the squeeze valve body as hereinbefore described in connection with annular space 77. Valve body 78a is provided with longitudinally extending slots 85a and longitudinally extending ribs 84a interconnected preferably integrally, at their inner surfaces by a continuous, imperforate, elastic sheet or tube portion as indicated. Formed in each of the elastic ribs 84a is a series of vertically spaced, radially extending slot-like holes R', cross sectional views of which are clearly evident in Figures 20a and 21a. The holes are so formed in the spaced ribs that the circumferentially adjacent holes of adjacent ribs combine to form a circumferentially aligned series of holes. Through each of the sexies of circumferentially aligned holes is arranged a respective steel ring R of round cross section and annular shape, with freedom for radial movement of the ring and aligned holes relative to one another sufcient to allow radial movement of the ribs 84a. As indicated in Figures 20 and` 20a, n'ngs R will be disposed at the inner boundaries of their respective holes R' when the squeeze valve is in normal or open position, and as indicated in Figures 2l and 21a, the rings will be disposed along the outer boundaries of their respective holes R when the squeeze valve body is in inwardly exed or closed condition. It will be noted from an examination of Figures 21 and 21a that rings R effectively prevent complete inward ilexure and collapse of the squeeze valve body by limiting the inward movement of the ribs and preventing the flattening or departure from circular shape of the body. Functioning and construction of this modiiied type of squeeze valve body is in other respects similar to or identical with that hereinbefore described with respect to squeeze valve body 78.

In order to show clearly the electrical connections between the various parts of the apparatus of this invention without unduly complicating the drawing, some of the electrical leads or circuits are diagrammatically shown as dashed lines located outside the sectional views of the apparatus, as in Figures 2 and 3, for example. In the actual construction of the apparatus, the electrical connections herein shown in dashed lines on the outside of the drill collar are insulated and are run through suitable fluid-tight channels or ducts inside the metal drill collar and sub.

Earth path conductivity measuring current is supplied to the bit from the control apparatus in container 26b through a lead 140 which is electrically connected to the metal of an insulated bit sub 32 at a suitable place, such as at point 170 (see Figure 3). The apparatus of the invention includes a means for detecting drill bit trouble such as drill bit wear beyond a predetermined amount, and excessive drill bit temperature. This means is so devised that upon occurrence of drill bit trouble of the character mentioned, the normal logging signals will be interrupted, thereby giving or presenting an indication of the occurrence of said trouble. The mentioned means includes a device in the form of a permanent magnet electric generator and thermosensitive circuit breaker for producing a positive indication of drill bit wear not in excess of the predetermined amount, and of drill bit temperature below a predetermined value. The invention also provides a method or procedure of operation whereby the particular type of drill bit trouble may be ascertained, as will be more fully explained hereinafter. The drill bit trouble detecting means located within the dashed line rectangle 9 of Figure 3 is shown more in detail in Figures 9 and l0.

Referring to Figures 9 and 10, a portion of one of the bit cones is shown with part of a cone tooth 116. Under normal operation this cone 115 rotates around a shaft 117 while the teeth of the cone exert their milling and chipping action on the bottom of the borehole in the process of drilling deeper. One or more of the outer teeth 116 are each provided with a small cylindrical magnet 118, preferably made of a highly magnetized alloy such as alnico, and provided with an external screw thread 118a to engage in a corresponding threaded bore of tooth 116. In the body 119 a bit 1S opposite the permanent magnet 118 is provided a coil 120 and a thermosensitive or maximum temperature circuit breaker 121. Obviously coil 120 and magnet 118 cooperate to form a permanent magnet generator operating to pro duce an alternating current voltage while cone 115 is rotating. A lead 122 is attached to one side of the circuit breaker 121, while the other side of the circuit breaker is connected to a terminal 167 of coil 120. The other terminal 168 of coil 120 is grounded to the metal of the drill bit. To permit passage of a generated electric current from coil 120 of the generator through an insulated conductor to entry lead 123 in the control component in container 26h, the following provisions are made. When bit 15 is screwed into bit sub 32, an annular rubber gasket 124 is in place between the two. This gasket contains a concentric metal ring 125 (Figure 9) which is positioned opposite a corresponding metal ring 126 in the bit sub 32 and metal ring 127 in the shank of bit 15. Metal rings 126 and 127 are mounted in annular insulating rings 128 and 129 recessed into the adjacent ends of the bit sub 32 and bit shank. When bit 15 is screwed into place, it will be obvious 11 that, regardless of its nal angular position above the axis of the bit sub 32, there will be a continuous insulated circuit from lead 122 to lead 123:: through the ring 125 in gasket 124.

Figure shows diagrammatically the electrical circuits utilized in the operation of the apparatus shown in Figures 2 and 3. The electrical equipment and circuits present within control components 26 in container 26b of Figure 2 are shown schematically in Figure 10 within the dashed rectangle 26a. Drilling fluid driven turbine 37 drives through shaft 38 an electrical generator 39, a large-ratio gear reducer 40, and a cam wheel 42, as described previously. Output lead 67 of generator 39 `is connected through lead 50 to the excessive torque switch or cut-out device in chamber 54 and from there through lead 131 to the excessive weight switch or cutout device in chamber 55. The output terminal of the excess weight switch device in chamber 55 supplies the voltage from the generator to the control component 26 in container 26b through input lead 53. From input lead 53 electric power is continuously supplied to the motor 91 of electrically driven pump 89 through leads 132 and 95 in the absence of excessive torque or excessive weight on the drill collar. Thus pump 89 is adapted to pump control fluid from reservoir 79 through passageway 80 into annular space 77, as shown in Figure 2, or annular space 77a, as shown in Figures 20 and 21.

A portion of the output of `the generator 39 is applied through suitable electrodes to an earth path adjacent the drill hole, as hereinafter more fully described, and the magnitude of the current flowing through said earth path at a given voltage is indicative of its conductivity, and is a measure of that conductivity. Under normal operating conditions inthe absence of suitable speed regulating means, the speed of turbine 37 varies with the velocity or rate of flow of the drilling fluid through the drill collar, and consequently the voltage of generator 39 is subject to considerable variation. If this voltage were directly applied to the earths formation through said electrodes, the resulting current would give unreliable results, since the value of such current would depend not only upon the conductivity or resistivity of the formation, but also upon the applied voltage which would, in turn, be dependent upon the velocity or rate of circulation of the drilling fluid stream. In order, therefore, to eliminate the effect of the resultant voltage fluctuation of generator 39 on the earth-path current, the output of generator 39 is applied to a voltage regulator indicated generally at 134 and which is adapted to translate a fluctuating input voltage into a constant output voltage.

Voltage regulator 134 is of conventional design and may be constructed in many different ways. Only one suitable embodiment is shown by way of illustration in Figure 10 and will be described hereinafter. One of the input terminals 133 of the voltage regulator 134 is connected to the generator 39 through the lead 53, while the other terminal 12917 which is grounded is connected to the generator through a return ground circuit. The regulator comprises a ballast tube 136 in series with a resistor 137 and connected across the before-mentioned input terminals 133 and 129b. The ballast tube may be an incandescent lamp or any resistor the resistivity of which increases with the current passing through the resistor. Thus, a substantially constant current passes through tube 136 in series with resistor 137, said current having a value substantially independent of the input voltage applied to the regulator. Consequently the output voltage drop across resistor 137 will be substantially constant.

The voltage drop thus appearing across resistor 137 is applied to a closed circuit comprising, in series with lead 13S, a stationary contact 143, a movable contact 138 carried on one side of a bimetallic strip 144, a heater coil 139, a lead 140, the insulated portion of the drill collar consisting of the bit sub 32, and the bit 15, the

before-mentioned earth path formed by the portion of the earth formation surrounding the borehole between the bit 15 acting as one electrode and the drill collar 24 above the insulation 28 acting as the other electrode, to which the before-mentioned terminal 129b is grounded. Since the voltage derived from across the resistor 137 is substantially constant, the current in the beforedescribed circuit and the before-mentioned `earth path depends substantially entirely upon the resistance or conductivity of said path. It is desired to transmit to the top of the borehole a signal representing the magnitude of said current, and this is accomplished by the following described apparatus.

The above-mentioned earth formation path current generates heat in heater coil 139 which, in turn, heats bimetallic strip 144, thereby causing the latter to bend and interrupt the circuit between contacts 138 and 143. When the current ow is thus interrupted, heater coil 139 and bimetallic strip 144 will cool and the latter will return to normal position, thereby reestablishing the circuit between contacts 138 and 143. The process of heating and cooling is thus automatically repetitive, the bimetallic strip 144 repeatedly bending to and fro, and the intervals between or the repetition frequency of such bending and the consequent interruption and closing of the circuit depending upon the magnitude of the current passing through heater coil 139, and consequently upon the conductivity of the before-mentioned current path tllrougl't"` the formations surrounding the borehole between theibit 15 and the portion of the drill collar 24 above the insulation 28.

The bimetallic strip 144 is provided on one side with a contact 138 positioned opposite the stationary contact element 142, as hereinbefore described, and also on the opposite side with a contact 145 insulated from the bimetallic strip 144 and positioned opposite a stationary contact 146, the arrangement being such that when the contacts 143, 138 are in contact with one another, the contacts 145, 146 are separated or out of contact with one another, and vice versa. The assembly comprising heater coil 139, bimetallic strip 144, and contacts 13 8, 143, 145 and 146 is contained within an enclosure illustrated at 141, and is known in the trade as an Amperite tube.

As beforedescribed, the bending motions of bimetallic strip 144 will alternately make and break the contact between the contacts 138, 143 and the contacts 145, 146 at time intervals or at a frequency depending upon the conductivity of the before-mentioned earth path, and hence the formation being drilled. Whenever contact is made between contacts 145 and 146, current from generator 39 will ow through input lead 53 and leads 132, 147, 148, 149 and 150 to the contacts of a relay 151. When this relay is in a closed condition the current will ow from lead 150 through the relay contacts and armature, and thence through lead 152 to the armature and contacts of a minimum voltage cut-out relay.153. When the latter relay is closed the current will pass from lead 152 through the armature and contacts of the relay, and through leads 96 and 96a to electromagnet 94 of valve 92. With both relays 151 and 153 closed, the power supply from generator 39 will therefore furnish time spaced pulses of electric current to electromagnet 94 to close valve 92 at a repetition frequency corresponding to that of the operation of Amperite tube 141. Closing of valve 92 while pump 89 is running will cause an increase of control uid pressure in the annular space 77 which in turn will cause the squeeze valve body 78 to ex or close from the condition illustrated in Figure 7 to that shown in Figure 8, and thereby produce a restriction in the drilling iluid stream path and a localized increase in resist ance to the llow therethrough of the drilling fluid. Automatic opening of valve 92 at the termination of each pulse of electric current through electromagnet 94 allows automatic return of the squeeze valve body to normal condition, removing the restriction in the drilling fluid stream. The localized increase in pressure drop across the squeeze valve which is utilized as a pressure-rise signal can be almost immediately detected at the earths surface, since it requires an increased pump pressure to overcome this resistance. Thus each `electric current pulse transmitted to the electromagnet 94 of valve 92 will cause creation or propagation of a corresponding pressure-rise signal in the drilling uid stream Vin the drill string which is transmitted to the pump at the earths surface. The repetition frequency of said electric current pulses represents or is a function of the conductivity of the formation being drilled and consequently said conductivity may be determined by measuring the repetition frequency of the pressure-rise signals in the drilling uid stream at the earths surface. It is thus apparent that by means of the present arrangement there is eliminated the necessity of an electrical conductor extending within the borehole being surveyed from the drill collar to the earths surface.

The purpose of relay 153 is to provide a minimum voltage cutout in the system responsive to the input voltage from the generator lead 67, to which the relay winding is connected for energization via leads 50, the excess torque measuring device in chamber 54, lead 131, the excess weight measuring device in chamber 55, leads 53, 132, 147 and 157. When, during the process of drilling, a washout or leak is developing in the drill pipe, it is of extreme importance that the driller be warned of this condition. Two alternate devices have been provided for this purpose in this invention. The first one is the beforementioned minimum voltage cutout relay 153, and the other will be particularly described hereinafter. It is obvious that the speed of rotation of turbine 37 and, consequently, the output voltage from generator 39, depend on the rate of drilling uid flow through turbine 37. Whenever part of the drilling fluid stream is diverted through a washout or leak in the drill pipe above the turbine the rate of drilling fluid ow through turbine 37 decreases, and hence the output voltage of generator 39 will decrease. When this occurs, relay 153, which is responsive to a predetermined decrease in the generator voltage, will drop out and open the circuit to the magnet 94 of valve 92, thereby providing the driller with a warning signal in the form of interruption of pressure-rise signals and the graphical translation thereof at the earths surface. To ascertain that this interruption is caused by `the opening of relay 153, the driller may increase the speed of pump 426 at the surface and attempt to reacti- `vate the signalling circuit through the magnet of valve 92 by sending an increased flow of drilling iiuid through turbine 37 suilicient to reclose relay 153. When this causes resumption of pressure-rise signalling, the driller will then know the previous interruption was due to lack of drilling uid reaching the turbine and will take corrective measures accordingly.

An alternative procedure and apparatus for the purpose of detecting a washout or leak in the drill pipe is provided by the invention. Included in this apparatus is the aforementioned cam wheel 42 driven by the low-speed output shaft 41 of large ratio gear reducer 40. Whenever cam wheel 42 has completed one revolution, it means that the turbine and generator combination to which it is conencted has made, for instance, one million revolutions. Whenever cam 43 actuates spring 44, contact is made between spring 44 and contact 45, which completes the circuit from generator 39 through leads 67 and 159, spring 44, contact 45, leads 160, 113a and 96a to the electro magnet 94 of valve 92 to the return ground circuit.y A drilling lluid pressure-rise signal of comparatively long duration will therefore be caused by the valve 92 each time cam wheel 42 makes one revolution, thereby providing signals at the surface which may be, and are, translated into an indication of the rate of drilling uid ow through the turbine by means more fully described hereinafter. An arrangement will be described hereinafter for producing another indication representing the rate at which drilling iluid is being pumped into the drill string. Under normal operating conditions, i.e., in the absence of any leaks or washouts, these two indications are equal, since the amount of drilling fluid pumped into the drill string is equal to the amount that passes through the turbine over a given period of time. However, if a leak develops in the drill pipe, a portion of the uid flow is diverted from the turbine, and consequently the rate of fluid ow through the turbine is smaller than that of the uid being pumped into the drill string. Thus when the -rst indication is larger than the second, the difference between said indications represents the amount of drilling uid diverted from the drill string through a leak or washout over said given period of time.

Referring further to Figures 2 and l0, output lead 67 of generator 39 is connected through leads 50 and 68 to metal insert 69 of the inclinometer switch device 70. Whenever the drill string is not rotating and the drill collar is within a predetermined number of degrees of a vertical attitude, brush makes contact with insert 69 as hereinabove noted. When this is the case, current from lead 68 will pass through the pendulum and through suspension joint 73 to lead 161 and from there to control component 26. From lead 161 the current passes through a resistor 162 and leads 163 yand 164 to the coil of relay 151, thereby closing the logging signal circuit previously opened when the permanent magnet generator was rendered inactive by lifting the bit off the bottom or by stopping rotation of the drill string.

It is thus apparent that in order to ascertain whether or not the borehole has deviated from vertical more than the predetermined amount, it is necessary for the driller to stop the rotation of the drill string while continuing circulation of the drilling fluid. If the deviation of the borehole is less than a predetermined amount from the vertical, the above-described circuit energizing the relay 151 is then closed and valve 92 is again intermittently energized in accordance with the conductivity of the formation, thus causing resumption of transmission of pressure-rise signals to the top of the borehole. If, however, while maintaining normal drilling fluid flow, rotation of the drill string is stopped and no pressure-rise signals indicating the formation conductivity are received at the earths surface, it is evident that the circuit energizing relay 151 has been inerrupted and consequently the inclination of the borehole exceeds the predetermined number of degrees from the vertical. The permissible deviation is determined by the relative areas of brush 75 and insert 69, and the length of pendulum 72, in an obvious manner.

Consider now the bit trouble warning or indicating device shown within dashed-line rectangle 166 in Figure 10 and comprising the previously described permanent magnet generator. Rotation of the bit cone and consequently also of magnet 118 past coil 120 will generate an alternating electric voltage in coil 120. Terminal 168 of this coil is grounded to the metal of the main body of the bit. Alternating voltage generated in coil 120 will be applied from terminal 167 through thermosensitive circuit breaker 121 to lead 122 and thence through contact rings 127, 125 and 126 and through leads 123a and 123 to control component 26, where its current is rectified by means of a rectifier 168 and thence passed through lead 164 to the coil of relay 151. The current return circuit from the grounded terminal of the coil of relay 151 to terminal 168 of the generator coil 120 is through the drill collar, the drilling uid near adaptor 33 and the stationary body of the bit. Since the bit is insulated from the drill collar, there is a small amount of resistance, usually of the order of ohms or less in the drilling fiuid between the metallic body of the bit and the portion of the drill collar above the insulated section. If the resistance of the coil of relay 151 and the resistance of the pickup coil is made high, say several thousand ohms, then this additional resistance is negligible by comparison. Of course, in some cases, such as when oil base drilling uid is used and the formation is of high resistance, it may be desirable to provide a second slip ring contactor arrangement such as that shown at 125 in Figure 9 for the ground return circuit between the coil 120 and the coil of relay 151 to lower the circuit resistance in an obvious manner; but to simplify illustration this second contacter has not been shown in Figure 9. Whenever drilling is in progress and the bit is not worn far enough to remove magnet 118, the current generated ,by the permanent magnet generator will keep relay 151 closed so that the signalling portion of the apparatus can function normally. Whenever the bit is worn beyond the point where magnet 118 is located, or whenever the temperature of the bit increases beyond a predetermined point so that breaker 121 opens the circuit, relay 151 will open, and the interruption of normal signalling will indicate to the driller that either the bit is worn too far, or that it is becoming overheated. If the drilling is stopped for a short period, allowing the bit to cool, and drilling is resumed, resumption of normal signalling will indicate closure of the breaker and that excessive bit temperature is the source of the trouble. Failure of signalling to resume will indicate a worn-off bit. Repeated signalling interruption caused by excessive temperature would indicate a stuck cone or the like and indicate the necessity of corrective measures. Thus the permanent magnet generator is seen to act as an effective bit wear detector and the thermosensitive circuit breaker as an excessive bit temper-ature detector.

The maximum Weight cut-out device in chamber 55 and the maximum torque cut-out device in chamber 54 have the function of informing the driller whenever the drill collar is subject to abnormal and dangerous stress. It is apparent that whenever an abnormal torsional stress develops in the drill collar, the resultant torsional strain causes the portion thereof comprising the insulating material 58 to become displaced through a rotational angle with respect to the portion comprising the insulating material 59. Since the lower portion of rod 51a is fastened to the insulating material 58 and the upper portion of the rod 51b is fastened to the insulating material 59, it becomes apparent that as a result of torsional stress in excess of a predetermined amount the electrical contact between the extensions 60 and 61 is broken, thus interrupting the supply of electric current to the voltage regulator 134. The signalling operation is accordingly discontinued, and, since no signals are then transmitted to the top of the borehole, the driller becomes aware of an abnormal and dangerous mechanical condition existing at the bottom of the drill string.

Similarly, whenever the drill collar is subjected to excessive compressional stresses, the portion thereof comprising the insulation 59 is linearly displaced along the vertical with respect to the portion comprising the insulation 63. Since the lower portion of the rod 52a is fastened to the insulating material 59 and the upper portion of the rod 52b is fastened to the insulating material 63, it becomes apparent that as a result of the excessive compression the electrical contact between extensions 64 and 65 is broken, thus interrupting the supply of electric current to the voltage regulator 13'4. In a similar manner, as in the case of excessive torsional stress, the driller is apprised of an abnormal or hazardous mechanical condition existing at the bottom of the drill string. Resumption of signalling after raising the drill string slightly, and with the drill string rotating, would serve to indicate that the trouble lay in too much weight on the bit, or excessive torsional stress, and failure of signalling to resume under such conditions would indicate either permanent deformation of the drill collar beyond allowable limits, or damage to the magnetic generator 166, requiring withdrawal of the drill string.

The apparatus is provided with an emergency circuit or switching device, illustrated in Figures 2. and 10, which makes it possible to cause resumption of conductivity signalling when one of the warning or cut-out devices has disrupted the normal signaling operations of the apparatus. This emergency switching device is contained, in part, in an annular space 98 surrounding the drilling duid passage and comprises a suitable electric induction coil 99 wound around and separated from the drilling tluid passage 100 of the drill collar by a thin, nonmagnetic tube 101. A xed mechanical bridge 102 is provided across the internal drilling fluid passageway 100. This bridge, although capable of stopping large objects dropped down the interior of the drill string, still allows the drilling fluid and entrained grit to pass freely through holes such as apertures 103 and 104 therein. lhe other part of the emergency switching device s contained principally within a hollow space 155 in the drill collar body adjacent the annular space 98 and comprises an electromagnetically operated, normally energized and normally open, emergency relay 105 having an electromagnet 156, a contact bearing armature 110, and a fixed contact 111. Impedance coil 99 is connected in series with the winding of relay electromagnet 156 through lead 161a, as indicated in Figure 10. Whenever it is desired to close the emergency relay 105, an iron bar 106 provided with vertically extending ribs 107 (see Figure 2), is dropped from the surface of the earth down inside the drill string where it comes to rest on bridge 102 within tube 101 and coil 99. The presence of this mass of iron inside coil 99 changes the self-induction and impedance of coil 99 to such an extent that the pulsating electric current passing through the coil and by way of conductor 161a through electromagnet 156 (supplied to them from generator 39 through leads 67 and 108, Figure V10), is reduced suiciently to permit armature 110 to fall under the iniluence of its spring and move into contact with contact 111. This closes an emergency electric circuit from the Amperite tube 141 through leads 149, 154, and 112 to and through the armature 110, contact 111, leads 113, 113a to lead 96a and electromagnet 94 of valve 92, thus shunting or bypassing the contacts of relays 151 and 153 and permitting the Amperite tube to again intermittently energize valve magnet 94 to again cause functioning of valve 92 and consequent conductivity signalling.

From the -foregoing `description of the information obtaining apparatus within and on the drill collar, and of the pressure-change signal producing or propagating apparatus, it is evident that in the course of normal operations, pressure-change signals in the form of relatively long pressure-increases, and of a relatively low repetition frequency, will be propagated in the drilling fluid stream in the drill collar, by action of the cam wheel 42, contact 45, an associated connections; these signals bearing information concerning the rate of ilow of drilling fluid through the drill collar at turbine 37. Also, pressurechange signals in the form of relatively short pressure-increases, and of a relatively high repetition frequency, will be similarly propagated by action of the Amperite tube and associated apparatus; the repetition frequency of these signals varying in accord with the conductivity of the earth path, but always being within a repetition frequency range that is above any possible repetition frequency of the signals indicating rate of ow of drilling fluid. Of course, any pressure-rise signal of the latter type, being of long duration, blanks out or overrides the shorter pressure-rise signals that would otherwise occur during the period of propagation of the longer signal. Further consideration of the apparatus thus far described, and its operation, indicates that the pressure-change signals of the two different repetition frequencies are cap-able of carrying tothe top of the borehole information concerning several types of conditions within the borehole and adjacent the lower end of the drill string. For example, one type of condition is drill bit cone wear beyondv a point where the permanent magnet generator functions to maintain relay 151 closed, a second type of condition being that of conductivity of the aforementioned earth path. Also, the repetition frequency of the signals in the higher frequency range is varied in accordance with variations in one type of condition; and those signals may be interrupted in response to occurrence of another type of condition, such as excessive drill bit wear, but resumption ofthe signals may be induced through suspension of drilling (by the action of pendulum 72, which is responsive to another type of condition, namely, borehole deviation, but only during suspension of drilling). The system thus permits the driller, by procedures hereinafter described, to secure, during drilling and during short pauses in the drilling, valuable information concerning several different types of conditions in the vicinity of the drill collar, the information being conveyed to the driller by sense receptive indications such as by visual indicators and by aural alarms, records and the like.

Consider now Figure 1 and the equipment located at the top of the borehole for detecting and translating the pressure-rise signals caused by the intermittent flexing of valve body 78. These pressure-rise signals are detected by means of an appropriate pressure-change sensitive device in the form of a detector or transducer means 200. The detector comprises a housing member 201 hydraulically connected to the discharge pipe 202 and provided with a flexible diaphragm 203, said diaphragm being arranged to fiex or move in response to any change in the pressure in the discharge pipe and hence in the drill string. The motion of the diaphragm is translated into corresponding variations of an electric current by means of a suitable transformer indicated at 204 and forming part of the transducer means. It is, however, apparent that any other suitable arrangement for translating pressure changes in the drilling fiuid into a variable electric current may be used, as, for instance, the one illustrated in the patent to Arps, No. 2,524,031. Transformer 204 comprises a stator 205 and a movable armature 206 rigidly connected to the center of diaphragm 203 and arranged to move with the diaphragm. The stator comprises a central core 207 and two U-shaped core elements 208, 209 forming a rigid structure provided with two air gaps 215 and 216, air gap 215 being in close proximity to armature 206. Core element 209 carries a winding which is in series with an alternator 217, the arrangement and construction of the transformer being such that when armature 206 is removed from the air gap, the magnetic flux passing through core 207 is extremely weak, and there is substantially no electromotive force induced in a secondary winding 218 carried by the core. When the armature 206 moves nearer to the air gap 216, a corresponding increased voltage will be generated in secondary winding 218, and this voltage is amplified in an amplifier 219 and subsequently rectified in a rectitier circuit 220. The rectifier circuit 220 may be of any desired type but is illustrated in Figure 1 as including a full-wave rectifier. Rectifier circuit 220 converts the alternating current output from amplifier 219 into a direct current, the voltage of which is proportional to the voltage generated in secondary winding 218. The rectier circuit comprises a step-up transformer 221 and a double-plate diode 222. Although full-wave rectification occurs in the illustrated rectifier circuit, a half-wave rectifier circuit may be used if desired. A capacitor 225 and a resistor 226 are connected across the output terminals of the rectifier circuit as indicated, to eliminate ripple from the output of the rectifier circuit in a well known manner. The output terminals of resistor 226 are in turn connected to a band-piece filter 227, said filter having its output terminals 232 connected to a derivator 228. The derivator comprises a capacitor 229 and a resistor 230 as indicated in Figure 1, and is arranged to produce across its output 231 a voltage representing substantially the time derivative of the voltage supplied across termi- 18 nals 232. The derivator may be of any type well known in the art and in this particular embodiment has been chosen to be of the type described in the patent to Scherbatskoy et al., No. 2,099,536. The output of the derivator 228 is then passed to a variable threshold network 233.

lt is apparent that there is obtained across the output terminals of resistor 226 a voltage varying in magnitude in accordance with the pressure applied by the pump 426 to circulate the drilling fiuid. Figure 1l shows as an example the variation of such pressure with time under normal operating conditions, utilizing the signal transmission system provided by the means including valve body 78. These pressure variations can be represented as a summation of three separate components separately designated as slowly varying component, noise, and useful signal. By the term noise as hereinafter used is meant those components of the input to a gate or threshold circuit to be described, which are of lower amplitude and of higher frequency than the desired information bearing signal pulses.

It is well known that as the drilling progresses the average total pressure applied by the pump slowly increases due to the increase in the length of the circulatory system. Furthermore, the pressure undergoes slow variations due to changes in the circulation rate or the viscosity of the drilling tiuid. In Figure 12 this slowly varying component is shown as continually increasing as the drilling progresses.

The noise shown in Figure 13 is represented by random fiuctuations of the pressure in the drilling fiuid system, which is essentially a dynamic system having distributed elasticity and inertia. These fluctuations, as shown in Figure 13, are relatively small in amplitude and of relatively high frequency. However, whenever a formation containing gas is encountered by the drill bit, small amounts of gas may become entrained in the drilling fluid system. This increases its elasticity and may cause a considerable change in the magnitude of the noise fiuctuation.

Figure'14 represents the useful signals in the form of a succession of pulses, each of said pulses being caused by a corresponding electric current pulse applied to the electromagnet of valve 92. These pulses succeed each other at a variable frequency, and at any time during the logging operation the repetition frequency of said impulses represents the conductivity of the formation drilled.

In order to obtain a clear and distinct record of the logging signals being transmitted through the drilling fiuid from within the borehole, it is desirable to eliminate from the output across resistor 226 those components shown in Figures 12 and 13 and transmit only the useful component shown in Figure 14. This is effected as follows: The voltage across resistor 226, varying with time substantially as shown in Figure 1l, is applied to filter 227. Filter 227 is of a band-pass type and is designed to attenuate signal components of frequencies below 1 cycle per minute and above 1 cycle per second. Since the slowly varying component shown in Figure 12 contains frequencies below 1 cycle per minute and the noise component of Figure 13 contains frequencies above 1 cycle per second, both undesirable components will be substantially attenuated. Accordingly, there is obtained across the output terminals of the band-pass filter a signal comprising substantially the useful pulses as indicated in Figure 14 together with a relatively small proportion of noise The output of the filter is in turn applied to the derivator 228, the purpose of which is to sharpen the useful pulses and produce an output voltage which is the first differential of the pulses as shown in Figure 14 and which then appears substantially as shown in Figure 15. As shown in Figure 15, the useful pulses are characterized by a certain value m. In order to transmit the useful pulses and to eliminate the noise, the output of the 19 derivator is applied to a gate or threshold network 233, said lnetwork being characterized by a threshold having a value T (see Figure 15) such that M T m. Hence, only the signals of amplitude exceeding T appear across the output terminals of network 233. The voltage obtained from said ouput is graphically depicted in Figure 16. The details of the threshold network and its operation will be described hereinafter.

The pulses appearing in the output of the gate network 233 are in turn applied to the frequency responsive network 240, the latter network being adapted to produce across its output terminals 241 a D.C. voltage whose amplitude is proportional to the repetition frequency of the pulses derived lfrom the gate network 233. The frequency responsive network may be of any type well known in the art (see, for instance, A Counting Rate Meter for Radioactivity Measurements, published in General Radio Experimenter, vol. XXII, No. 2, 3, July- August, 1947, pages 1 7).

One of the output terminals of the frequency responsive network is directly connected to an input terminal of an amplifier 245 through a lead 246. The other output terminal of the network is shown to be connected through a switch 247 to a lead 248, which in turn is connected through a switch 249 to the other input terminal of the amplifier 245.

It is thus apparent that pulses applied to the frequency responsive network 240 produce across the output of said network a D.C. voltage representing or proportional to the frequency of the input signal, and said frequency is in turn indicative of or proportional to the conductivity of the formation adjacent the lower end of the drill string. This D.C. voltage is in turn applied to the grid 250 of the variable mu tube 251. The variable mu tube is of a type well known in the art and has the gridvoltage plate-current characteristic shown in Figure 17. It is apparent from Figure l7 that, if the voltage derived from amplifier 245 and applied to the grid has a value OK, the corresponding plate current has a corresponding value KL such that KL is equal to a function of 1/OK. There is thus obtained from the output 258 of tube 251 a current that is an inverse function of the voltage derived from amplifier 245. Since the latter voltage represents the conductivity of the formation being drilled, the current derived across output 258 represents the corresponding value of the resistivity of the formation.

The output of tube 251 is applied to a recorder 260 to produce a resistivity log of the borehole, i.e., a graphical indication in the form of a compound graph representing the variation of resistivity of the formations drilled through or traversed, with respect to time or depth of borehole. Such a graph is produced upon a lightsensitive record film 261 which is unwound from the drum 262 and wound upon the drum 263. A galvanometer mirror 264 positioned adjacent film 261 is arranged to reflect a beam of light from a lamp 265 onto the film 261 to produce thereon a trace 267 representing the resistivity log of the borehole. The mirror 264 is carried by a galvanometer coil which is connected to output 258 of tube 251. The unwinding action of drum 262 and the simultaneous winding action of drum 263 is effected through a shaft 268 driven by a gear box 269 which in turn is directly connected through a drum 270 and flexible cable to the travelling block 22 in the manner indicated, Thus, the record film 267 is moved in response to the downward movement of the travelling block 22 as it follows the downward movement of the drill string into the well, whereby the trace 267 may be correlated with the depth of the borehole in a manner now well known in the art. While a light-sensitive film and light beam apparatus have been disclosed as means to record the translated signals, it is evident that other conventional graphical recorders may be cutilized to pre- 20 sent a graphical record indicating variations of resistivity of the earth adjacent the drill bit.

Consider now again the subsurface equipment diagrammatically depicted in Figure 10, and particularly the voltage regulator 134 for translating the variable voltage derived from the generator 39 into a constant output voltage that is applied to the earth formation adjacent the drill bit through the Amperite tube 141. As explained hereinabove, the voltage across resistor 137 is maintained constant and substantially independent of the fluctuations in the output of the generator 39, said fluctuations being caused by variations in the rate of flow of the drilling fluid through the turbine. Assume, however, that the voltage regulator has been eliminated, which may be visualized, for instance, by replacing the ballast tube 136 with an ordinary linear resistor. In such event, regulator 134 will not act any more as a voltage regulator, and its output voltage derived from the lead 135 will increase (or decrease) with increase (or decrease) of the rate of flow of drilling fluid; and similarly, the pressure-rise signals in the drilling fluid in the drill string will correspondingly vary in repetition frequency. In order to make the recorded signal independent of the rate of flow of the drilling fluid, a compensating apparatus is provided at the surface, which apparatus is principally contained within the dotted rectangle 275 (Figure 1) and includes electric circuit elements which may be inserted between the output of network 240 and the input of amplifier 245 by means of switches 247 and 249. The compensating apparatus comprises a rheostat 276 having its input terminals connected to the network 240 through the switch 247 and having one of its output terminals 501 connected to a movable contact 277. The latter contact is rigidly attached to a rod 278 provided at its end with a ferromagnetic solenoid armature 279 movable within a solenoid winding 280 and suspended from a fixed support 300 by means of a spring 301. Winding 280 is connected through leads 281 to a turbogenerator 282 positioned within the drilling fluid discharge pipe 202 as indicated in Figure 1. It is apparent that any increase in the rate of flow of the drilling fluid will cause a corresponding increase in the output voltage of the turbo-generator. This in turn increasingly energizes the solenoid winding 280, which causes core 279 to move contact 277 in a downward direction against action of spring 301. Consequently, the voltage across the input terminals of amplifier 245 decreases, thus compensating the increase in voltage across the output of the network 240 caused by the corresponding increased output of generator 39 and reflected by an increase in the repetition frequency of the logging signals. It is thus apparent that whenever the drilling fluid rate of flow changes, the change in the voltage of generator 39 at the bottom of the borehole causes a corresponding change in the signal derived at the output 241 of the network 240, and in order to compensate for this signal change, turbogenerator 282 positioned at the top of the borehole operates through the solenoid 279, 280, the rheostat 276 so as to compensate the change and provide across the input terminals of amplifier 245 a voltage that is substantially the same as if the rate of flow of the drilling fluid had not been altered.

Consider now again the gate network 233. Referring to Figures 1, 15, 18 and 19, this network is characterized by a threshold value T which is smaller than M and larger than m, M being the magnitude of the useful signals, and m being the normal maximum magnitude of the noise signal. It is apparent that the values M and m vary as the drilling progresses. The value M depends upon such factors as the rate of flow of drilling fluid and the drilling fluid viscosity and density, andthe value of m is particularly sensitive to the presence of gas in the drilling fluid.

It is thus apparent that under some conditions, the value Amay increase to a. value almost equal to the value of M. In order to make certain that under such conditions the residual noise signal of Figure 13 is always eliminated, it is desirable to maintain the threshold value T so that the difference (M-T) is substantial but not unnecessarily large. Since the value of M varies as the drilling progresses, it is desirable to correspondingly vary the threshold T so as to maintain the difference (M T) at its optimum value. Under such arrangement the threshold network will work most effectively, i.e., it will transmit all the useful signals and eliminate the noise In order, therefore, to obtain an effective threshold action, there is provided an automatic control for varying the threshold value T in response to the peak value M of the useful signals. A diagram of the variable threshold network is shown in Figure 18.

As shown in Figure 18, the threshold network comprises a triode 330 having its anode 332 connected through a resistor 333 to a voltage source 334. The grid 335 is connected to a cathode 336 through a circuit comprising the output of the derivator 228 in series with a battery 338 and a condenser-resistor element, said element consisting of a resistor 337 shunted by a condenser 339. The anode 332 is connected to the cathode 336 by means of a condenser 340 in series with a resistor 341. The terminal 342 of resistor 341 is connected to the terminal 343 of resistor 337 by means of a battery 344 in series with a rectifier 345. The other terminal of resistor 341 is connected to frequency responsive net work 240.

It is assumed that the triode 332 normally operates under operating conditions indicated diagrammatically in Figure 19. Figure 19 shows three diagrams that are separately enclosed within the dotted rectangles 350a, 351a and 352a, respectively.

The diagram within dotted rectangle 350a of Figure 19 shows the plate current grid voltage characteristic of triode 330. The abscissa represents the voltage eg applied to grid 335, and the ordinate represents the corresponding current Ip owing in the plate circuit of the triode through resistor 333. The point O represents the origin of coordinates. Of particular significance in this diagram are the point C representing the cut-off potential and the point A representing the grid bias. The magnitude of the grid bias Eg is represented by the segment AO, and the magnitude of the threshold potential T is represented by the segment AC. It is apparent that the voltage applied across conductor 231 of Figure 18 is superimposed upon and opposite to the grid bias. Consequently, if this superimposed voltage is less than T, it is below the cut-off potential of tube 332, and, conversely, if it is more than T, it is above the cut-off potential.

The diagram enclosed within the dotted rectangle 351a of Figure 19 represents the voltage derived across 231 and applied to the grid of the triode. The vertical axis of f coordinates represents time, and, since this voltage is superimposed upon the grid bias Eg of the tube, the time axis has been drawn at a distance Eg to the left of point O. The grid bias threshold voltage T is below the magnitude M of the useful pulses by a predetermined and small amount. The useful pulses are above the cut-off point C, and they produce corresponding plate current pulses as indicated in dotted rectangle 352a. The noise is completely cut ofi, since it is below the cut-off point C.

It is apparent that, in order to maintain the conditions illustrated in Figure 19, it is necessary to maintain the grid bias at a specific value Eg. Furthermore, it is important to consider in that connection that the value Eg depends on and is determined by the magnitude M of the useful pulses.

The relationship between M and Eg will be illustrated by a numerical example. Let the useful pulses M applied across the input 231 be 3 volts. Then the corresponding grid bias of tube 330 should be Eg volts. By

Areferring to Figure 18 it is seen that the grid bias is supplied by the voltage of battery 338 minus the voltage drop across the resistor 337.

Consider the closed circuit formed by resistor 341, battery 344, rectifier 345, and resistor 337. Let the voltage of battery 344 be 20 volts and the voltage of battery 338 be (Eg-P3) volts. Assume that each of the useful pulses M applied to the grid is equal to 3 volts and the amplified pulse across resistor 341 is equal to 23 volts. It is apparent that this amplified voltage opposes the voltage of battery 344 and causes a current to ow through said closed circuit. This current produces a voltage drop across the resistor 337, the amount of said voltage drop being -3 volts. Consequently, the grid bias of the triode is equal to the voltage of battery 338, i.e., (Eg-P3) volts, to which there should be added the voltage drop across the resistor 337, i.e., -3 volts, and there is obtained the desired value of Eg volts.

Referring to Figure 19a, should the magnitude of the useful pulses increase and assume a larger value M', then the magnitude of the grid bias will change to OA" in order to provide a new threshold value T such that (M'-T =(M-T).

Consider now Figure 19a showing the result of such an automatic adjustment. Figure 19a comprises three portions, 350b, 351b, and 352b, corresponding, respectively, to dotted rectangles 350a, 351e, and 352a of Figure 19. In the diagram 350b, the point A has been shifted to a new position A" such that AO represents the new increased grid bias Ffg, and AC represents the new increased value T of the threshold potential. Thus, in the arrangement shown the grid bias Eg of the tube increases (or decreases) in response to an increase (or decrease) in the magnitude M of the useful pulses. It is apparent when the grid bias increases (or decreases) the corresponding threshold potential increases (or decreases).

Refer now again to Figure 18 in order to see how the automatic control is effective in order to increase the grid voltage of triode 330 from the previous value E'g to a new value Eg in response to the increase in the magnitude of useful signal pulses from a previous value M to a new value M. Assume that each of the pulses of value M applied to grid 335 is now 6 volts (while previous M=3 volts). Then, after equilibrium is established, the corresponding voltage across resistor 341 is equal to 26 volts (previously it was equal to 23 volts). Since the opposing voltage of battery 344 is 20 volts, the corresponding resultant voltage that is rectified amounts to 6 volts. This voltage produces a current in the resistor 337, and the voltage drop across said resistor is 6 volts. Consequently, the grid bias of the triode is equal to the voltage of battery 338, i.e., (Eg-F3) volts, to which should be added the voltage drop across resistor 337, i.e., -6 volts. We obtain thus as the new voltage of the grid bias E"g=E'g-I-3-6=(Eg-3) volts. It is thus apparent that the grid bias of triode 330 has readjusted itself from its previous value Eg to a new lower value E"g=Eg-3 volts. Consequently, when the input voltage pulses increase above a certain value, the circuit readjusts itself in such a manner as to cause a corresponding increase of negative bias impressed upon the grid of triode 330.

The apparatus depicted in Figure 1 is provided with two alarms 360, 361 to provide siutable aural warning signals whenever the output current of amplifier 245 reaches a predetermined maximum value or decreases to a predetermined minimum value, respectively. The output of amplifier 245 is connected through leads 362 to a maximum relay 363 controlling alarm 360 and to a minimum relay 364 controlling alarm 361. Alarm 360 is actuated only when a conductivity measurements is greater than a predetermined value, and thus informs the driller of new and sometimes abnormal conditions encountered in the borehole, such as when highly conductive salt water bearing sands, salt formation or low resistivity shale is encountered. Alarm 361 is actuated only when a translated conductivity value, and hence the output of amplier 245, decreases below a predetermined value. This may occur whenever a highly resistive formation is encountered by the drill bit or when the signal producing circuit through valve electromagnet 94 is interrupted by the maximum torque switch or cut-out device in chamber 54 or by the maximum weight switch or cut-out device in chamber 55, or when either of relays 151, 153 is deenergized. Then the circuit through valve electromagnet 94 is interrupted by either of the devices in chambers 54, 55, or by either of the relays 151, 153, conductivity signalling is interrupted and no signals appear in the output of amplifier 245; and consequently alarm 361 will be set in operation by relay 364. When a highly resistive formation is encountered, however, the output of amplier 245 may only drop to a low value, yet sufficiently low to cause relay 364 to set alarm 361 in operation. This latter may mean that a potentially oilor gas-productive formation is encountered, and the driller will make sure of such condition by drilling slowly deeper for a limited time with reduced weight on the bit and reduced torque on the drill pipe (to make certain the maximum torque and weight cut-out switches are closed), in order to ascertain that the output of amplifier 245 is still maintained below said predetermined value at which alarm 361 is actuated. If this is the case, and if he desires to test the productivity of such a highly resistive formation, the drill string may be withdrawn from the hole and a drill stem tester run to test the drilled formation in a conventional manner. If the drill stem test reveals sutiicient productivity, the casing may be run Y and the well completed as a producer in a conventional manner.

It is obvious then, that this invention makes it possible to complete a well immediately upon reaching a potential pay zone or formation and before the well may have been drilled inadvertently too deep, into bottom water, as is frequently the case when conventional drilling and logging practices are used. A subsequent shut-off of such bottom Water is often very costly and diicult to achieve.

When continued slow drilling with reduced weight on the bit and reduced torque on the drill pipe fails to restore the output of amplifier 245 above said predetermined value, the driller concludes that either one of the relays 151,01' 153 is deenergized.

When the circuit to the magnet of valve 92 is disrupted by relay 153, it may be an indication that a washout or leak is beginning to develop in the drill pipe. The latter is one of the aforementioned types of conditions. If such is the case, by increasing the rate of pumping of drilling uid, the electrical circuit through the contacts of relay 153 may be reestablished, resulting in resumption of pressure-rise signalling, and in that case the driller recognizes this as the cause of the trouble. Since continued drilling with a washout in the drill string may easily lead to a complete break in the drill p-ipe and a serious fishing jog, the driller will in such case withdraw the drill string from the borehole and replace or repair the damaged joint or connection.

When increased pumping rate fails to cause resumption of logging signalling, the circuit to the magnet of valve 92 must have been disrupted by relay 151 (with the continuation of slow drilling with reduced weight and torque on the bit), which may be an indication that the bit teeth are worn to the point that the magnets 118 are completely removed, or that the roller has ceased to rotate, or that the bit has been overheated so that thermosensitive circuit breaker 121 has disrupted the circuit to relay 151. In order to verify this point, the driller lifts the bit olf bottom and stops the rotation of the drill string, while continuing normal circulation of the drilling fluid. If the hole does not deviate more than a predetermined number of degrees from the vertical, the inclinometer switch device 70 will then cause resumption of signalling by reactivating relay 151 through leads 161, resistor 162, and lead 163, thereby indicating drill bit trouble in the form of a worn-out or overheated bit. lf such a procedure fails to restore the output of the amplifier 245 above said critical value, that is, if normal signalling is not resumed, either the hole may be deviating more than the allowable angle from the vertical, or the driling bit may be seriously worn or overheated. Excessive deviation may be checked by raising the bit to a previous position at which signalling was normal. If signalling is then resumed, it is obvious that borehole deviation has exceeded permissible limits and corrective measures may be taken. If, however, with the bit on the bottom signalling is resumed with the drill not rotating, it is evident that the deviation is within permissible values and the trouble lies in excessive tooth wear or overheating of the bit. Which of the latter types of condition causes cessation of signalling during bit rotation may be determined by suspending drilling for a suflicient time to permit the bit to cool and the circuit breaker 121 to close, whereupon if drilling is again commenced and signalling is resumed, the fault obviously lay in overheating; whereas, if upon resumption of drilling no signals are received, excessive tooth wear is the cause. Thus, the driller may ascertain which of the three types of condition exists. lf, under the just stated conditions signalling is restored upon resumption of drilling but is again quickly interrupted, it is evident that the drill bit is overheated and that a serious condition exists. The overheating condition in the absence of reduced drilling liuid circulation through a washout may be caused by the fact that one of the cones of the drill bit is stuck so that the normal rotating and chipping motion of the cone is replaced by a grinding or scraping motion which usually causes an excessive rise in temperature of the bit. If such a condition is not detected early the cone may wear down and break olf, thereby causing a troublesome fishing job. In either the event of excessive wear of the drill bit or a struck cone the drilling progress is usually subnormal. A checkup on the drilling rate will therefore provide the driller in this case with an additional indication or check on the cause of the trouble.

It will be obvious from the above that the various alarm and control devices in this invention have provided the driller with a positive and complete warning system of all critical conditions which in conventional rotary drilling are the cause of most, if not all, of the mechanical trouble and fishing jobs experienced. The practice of this invention will, therefore, make it possible to eliminate most of the mechanical failures by provisionof timely sense perceptive indications of malfunctioning and a procedure for determining the source of incipient failure whereby timely corrective measures may be taken before failure or serious trouble results. If, in case of an emergency, it is necessary to drill ahead in spite of an adverse mechanical condition, or when it is desired to relog a previously drilled portion of the hole while the string is being withdrawn for one of the above mechanical reasons, the iron bar 106 may be dropped in the drill string from the surface which, when it comes to rest on bridge 102, will close a circuit, bypassing the contacts of relays 151 and 153, this bypass circuit including leads 154, 112, armature 110, contact 111, leads 113, 11311 and 96a, by deenergizing relay 105, thus making normal logging operations possible without the use of the auxiliary information obtaining or control devices as hereinabove explained.

The arrangement schematically depicted in Figure l also provides an alternative signalling device working in conjunction with the subsurface equipment for indicating the presence and magnitude of a washout in the drill pipe. Under normal operating conditions, that is, in the absence of a washout, the rate of ow of drilling fluid into the drill string is equal to the rate of flow through the turbine in the drill collar. However, if a leak develops in the drill pipe, a portion of the fluid flow is diverted from that turbine, and consequently the flow of the fluids through turbine 37 decreases and is smaller than that through discharge pipe 202. By measuring the difference between the rates of flow, the magnitude of any leak may be determined. The rate of flow of drilling fluids through turbine 37 is measured by means of the subsurface equipment utilizing the cam wheel 42 and the spring 44 referred to hereinabove. Whenever cam 43 reaches spring 44, connection is made between lead 159 and contact 45 which is connected through lead 160 to the magnet of valve 92. A pressure rise signal of comparatively long duration will therefore be produced in the drilling fluid stream each time the cam wheel 42 makes one revolution, thereby providing a correspondingly long signal at the earths surface. The repetition frequency of, or time interval between, these extra-long signals indicafes, or is a measure of, the rate of fluid flow through the turbine in the drill collar. These signals are detected at the earths surface by means of detector or transducer means 200, and appear across the output terminals of resistor 226 in the form of long rectangular pulses, the duration of each of said pulses being considerably longer than the duration of the useful pulses referred to hereinabove and illustrated in Figure 14, and of much lower repetition frequency.

Band pass filter 227 is designed to attenuate these pulses and eliminate them from further transmission through the first signal translating network, including derivator 228, threshold network 233 and network 240. These extra long pulses are, however, passed by a band pass filter 600 into a second signal translating circuit including a slow-acting relay comprising electromagnet 371 arranged when energized to attract 'an armature 372, thereby breaking a local circuit comprising a battery 373 normally energizing an electromagnet 374. The purpose of band pass filter 600 is to eliminate the pump stroke noises indicated in Figure 13 and also to eliminate the higher repetition frequency logging signals indicated in Figure 14, and the very slow pressure fluctuations indicated in Figure l2. This band pass filter 600 is therefore designed to pass pulses of repetition frequencies of the order of one-half cycle per minute, and to eliminate pulses or waves of other frequencies. Thus, it is seen that the second signal translating circuit is arranged to receive and pass signal pulses of repetition frequencies within a lower range below the higher repetition frequency range in which the earth path conductivity logging signal repetition frequencies lie.

Referring again to Figure l, the electromagnet 374 cooperates with an armature 375 connected to a member 376 arranged -to actuate a ratchet wheel 380 in an obvious manner. Whenever the electromagnet 374 is energized, it attracts armature 375, thereby rotating ratchet wheel 380. Whenever a long pulse occurs along the terminals of band pass filter 600, the electromagnet 371 is energized, thus causing opening of the circuit supplying current to electromagnet 375, and thereby allowing a spring 381 to retract rod 376 and cause it to engage a succeeding tooth of ratchet wheel 380. After an interval of time, the pulse applied to electromagnet 371 disappears, and thus electromagnet 371 drops armature 372 which again closes the circuit of battery 373 and the latter again energizes electromagnet 374. Electromagnet 374 then attracts armature 375 and moves ratchet wheel 380. It is thus apparent that the angular displacement of ratchet wheel 380 represents, or is proportional to, the number of pulses applied to electromagnet 374, and hence represents, or is proportional to, and serves as a physical and mechanical indication of, the amount of drilling fluid that has passed through turbine 37 at the bottom of the drill string in a period of time required for that displacement; and hence is an indication of the rate of flow of drilling fluid through the drill collar and the lower end 'of the drill string. On the other hand, the amount of drilling fluid pumped into the drill string is proportional to the number of revolutions of the motor 400 which drives pump 426. The shaft 401 of motor 400 drives a large ratio geared speed reducer 402 provided with an output shaft 403. It is thus apparent that the angular displacement of shaft 403 represents, or is proportional to, the amount of input drilling fluid that has been pumped into the drill hole in the time required for that displacement, and hence is an indication of the rate of ow of drilling fluid into the drill string.

A shaft 404, driven by tne ratchet wheel 380, and shaft 403 are in turn applied through respective gear sets 405 and 406 to a differential gear box 407. The number of teeth on ratchet wheel 380 and the ratios of the gearing and speed reducer 402 are chosen on the basis of experiment so that under normal, trouble-free conditions, shaft 403 will rotate through one revolution during the interval required for turbine 37 to rotate cam wheel 42 through a number of revolutions equal to the number of teeth on ratchet wheel 380. Thus, in normal operation shafts 403 and 404 will each complete one revolution in the same period of time, and differential gear box 407 may thus be such that if gear sets 405 and 406 are of equal ratio, the output shaft 408 of the differential gear box will remain stationary when its input shafts rotate at the came speed. The output shaft 408 of the differential gear box is provided with an indicator 409 arranged for movement over a circular scale, indicated in part at 410. The angular displacement of shaft 408 from an initial position thus represents, or is proportional, to the difference between the angular displacements of shafts 403 and 404, and consequently represents and is proportional to the difference between the rate of flow of drilling fluid supplied by pump 426 to the drill string and the rate of flow through turbine 37. Under normal operating conditions these two amounts are equal to each other, and consequently the indicator 409 is normally approximately or relatively stationary. When, however, a leak develops in the drill pipe, a portion of the drilling fluid flow is diverted through said leak, and the amount of fluid flowing through turbine 37 is smaller than the amount delivered by the pump 426. Consequently the angular displacement of shaft 403`lecomes larger than the corresponding angular displacement of the shaft 404 and the difference is represented by angular displacement of shaft 408. It is thus apparent that extensive motion of the indicator 409 over the scale at 410 indicates a wash-out, and the amount of displacement of said indicator represents the amount of drilling fluid which has been diverted due to said washout. Calibration of the scale indicated in part at 410 may, if desired, be effected in an obvious manner, although such calibration is not necessary to full and complete practice and use of the invention. Obviously, too, any slight change or changes in the relative rates of rotation of shafts 403 and 404 due to changes in depth of the borehole, changes in viscosity of the drilling fluid, and the like, may be noted as slight, steady changes in the indications of indicator 409 and taken into consideration without affecting use and practice of the invention. Further, while there have been disclosed two mechanical indicating means for presenting physical indications of the rates of flow into the drill string and through the drill collar, respectively, and a mechanical indicating means for presenting a physical indication of the algebraic difference between the first two indications, it will be evident that electrical indicating means could readily be employed without departing from the concept covered by the invention. Further, since drilling fluid is pumped into the upper end of the drill string at an approximately uniform rate; it is evident that by noting any consistent decrease in the repetition frequency of the long pulse signals, as by noting any consistent decrease in the rate of actuation of ratchet wheel 380,

27 a leak in the drill string can be detected, While drilling is in progress as well as during periods of suspension of drilling. As soon as a leak is detected, drilling may be suspended and the leak corrected.

In this application only one preferred embodiment of the system according to the invention has been disclosed, and it will be apparent to one skilled in the art that the invention is not limited to that particular embodiment, but that many modifications may be made without departing from the spirit and scope of the invention.

What is claimed is:

l. In a logging system for an earth well borehole filled with drilling uid the combination comprising: a drill string including a drill collar adjacent the lower end thereof located in the earth borehole; means including a conduit and a pump acting to force drilling iluid to ow under pressure in a stream into and through said drill string and acting to produce a first physical indication of the inlet rate of ow of drilling fluid forced into the drill string; means in said drill string to produce an electric current flow through an earth path adjacent the lower end of the drill string, said current having a magnitude dependent upon the conductivity of said earth path, and to produce a series of relatively short pulses of electric current at a repetition frequency within a given repetition frequency range but of repetition frequency dependent upon the magnitude of said current ow; means in said drill collar including an electromagnetically actuated control valve to receive and utilize said pulses of electric current to produce pressurerise signals in said stream of drilling fluid at a repetition frequency normally equal to the repetition frequency of said received pulses; means including transducer means adjacent the surface of the earth acting lo receive and translate said pressure-rise signals in said stream of drilling fluid into electrical signal pulses of duration and frequency equal to those of said pressure-rise signals; a first electrical signal pulse utilizing means connected to admit said electrical signal pulse and including selective means to pass only such of said electrical signal pulses as are of repetition frequency within said given frequency range and also to produce an indication indicative of the repetition frequency of said last-mentioned electrical signal pulses and thus representative of the resistance of said earth path adjacent the lower end of the drill string; means within the drill collar to there make a measure of the outlet rate of ow of drilling lluid therethrough and produce a series of relatively long pulses of electric current at a repetition frequency dependent upon and indicative of said measure and in a lower repetition frequency range below said given repetition frequency range, and acting to apply said relatively long pulses of electric current to said electro-magnetically actuated valve for utilization thereby to produce correspondingly long pressure-rise signals in said stream of drilling uid; a second signal utilizing means connected to said transducer means and including selectivemeans acting to pass only relatively long electrical signal pulses of repetition rate within said lower repetition frequency range and acting to produce in response thereto a second physical indication of the outlet rate of How of drilling uid through the drill collar; and means acting to compare said rst and second physical indications of rate of flow of drilling uid and produce a physical indication of any difference therebetween, whereby during drilling operations within the borehole there is presented at the surface of the earth an indication of both earth path resistance adjacent the lower end of the drill string and any possible difference of rate of ow of drilling fluid into the drill string and through the drill collar indicative of a drill string leak.

2. In an earth well borehole logging system. the combination comprising: a drill string having a drilling liuid passage therethrough from top to lower end thereof; aA

'28 first means including a conduit and a pump to force a stream of drilling fluid to flow under pressure into and down through the drill string and also acting to produce a first physical indication of the rate of ow of drilling tliuid into the upper end of the drill string; a second means, at the lower end of the drill string, including means acting to determine a measure of the electrical conductivity of the earth adjacent thereto around the borehole and to translate said measure into a series of relatively short duration pressure-rise signals in said stream of drilling fluid, the repetition frequency of the short duration pressure-rise signals varying in accordance with said conductivity and being within a restricted repetition frequency range, said second means also acting to measure the rate of flow of drilling fluid through the bottom of the drill string and to translate said measure into a series of relatively long duration pressure-rise signals in said stream of drilling fluid, the repetition frequency of the long duration pressure-rise signals varying in accordance with the rate of flow of the drilling fluid through the lower end of the drill string and outside said restricted repetition frequency range; a third means, adjacent the 'top of the drill string and including pressure-rise signal transducer means arranged and acting to detect and transiduce said long and short duration pressure-rise signals into correspondingly long and short electrical signal pulses `of repetition frequencies the same as their respective pressure-rise signals, said third means also including a :signal channel means receptive of only said short electrical pulses of repetition frequency within said restricted repetition frequency range and a signal translating means acting to produce a graphical record from said short electrical pulses and indicative of the said conductivity, said third means further including a second signal channel means receptive of only :said long electrical signal pulses and a translating means acting to produce from said long electrical signal pulses a second physical indication of the rate of flow of drilling fluid through the lower end of the drill string; and comparison means arranged and acting to receive and compare said first and second physical indications and produce a third physical indication of the algebraic difference therebetween; whereby during drilling operations within the borehole there is presented at the surface of the earth a current record of both earth conductivity at the lower end of the drill string and any possible difference of rates of drilling fluid flow into the drill string and through the drill collar indicative of a drill string leak.

3. In a logging system for an earth well borehole in which a stream of drilling uid ows under pressure in a path through a drill string from the top to the lower end thereof at a locality within the borehole, and in which information secured within the borehole is transmitted to a point at the surface of the earth via pressure-rise signals propagated in said stream of drilling fluid for detection at said point, the combination comprising: a drill string and means including a pump and a conduit acting to supply drilling fluid at a normal rate in a stream to said drill string; primary means within the borehole adjacent the lower end of the drill string providing a pulsating current power supply, and a rst electric circuit powered by said power supply to produce and carry an electric current proportional in magnitude to the conductivity of an earth path adjacent said means; a second electric circuit powered by said power supply and including a circuit breaker means therein having contacts intermittently actuated by said electric current to open and close said second electric circuit to cause energization and deenergization thereof at a repetition frequency pro portional to the magnitude of said current, said second electric circuit also including in series with said contacts an electromagnet and rst and second sets of relay contacts; a drill bit at the lower end-of said drill string and electrical relay-including drill-bit trouble indicating means operable during normal drilling operations to maintain 

